In the current mobile communication system, such as LTE, it is common that communication between user equipment UE and user equipment UE is performed through a base station eNB by performing communication between the user equipment UE and the base station eNB; and, in recent years, various techniques have been proposed for the D2D communication in which communication is directly performed between user equipment UE and user equipment UE.
In particular, for the D2D communication in LTE, the following have been proposed: “Communication (communication)” for performing data communication, such as a push-type call, between user equipment UE and user equipment UE; and “Discovery (detection)” for causing receiving user equipment to detect transmitting user equipment UE by transmitting, from the user equipment UE, a discovery signal (discovery signal) including a predetermined ID, etc., (see Non-Patent Document 1). Note that it is assumed that the Communication is applied to the Public safety (police/fire service radio), for example.
For the D2D communication to be specified in LTE, it has been proposed that each user equipment UE utilizes a part of an uplink resource that has already been specified as a resource for uplink signal transmission from the user equipment UE to a base station eNB. Additionally, it has been proposed that a base station eNB assists for allocating a resource to be used in the D2D communication.